Porsche 964 engine reseal questions.
 

I'm completing a reseal on my 964 and thought I'd start a specific thread for advice rather than posting in others threads. Right now I'm in the disassembly stage and have a few questions.

Firstly, three of the tappets/followers have some pitting. It doesn't look bad to me or is it?http://forums.pelicanparts.com/uploa...1492766577.jpg
http://forums.pelicanparts.com/uploa...1492766598.jpg
http://forums.pelicanparts.com/uploa...1492766625.jpg

The thrust washers and shims behind the cam sprockets are not in the correct sequence and one thrust washer has the groove in the wrong orientation. Why did the factory specify the sequence and orientation it did?http://forums.pelicanparts.com/uploa...1492766862.jpg
http://forums.pelicanparts.com/uploa...1492766894.jpg

The cylinders were machined to accept a gasket at the last rebuild. This process appears to have weakened the edge and two cylinder bases have chips. Are these chips critical to sealing i.e. Does this mean new bases are needed for the two cylinders?http://forums.pelicanparts.com/uploa...1492767191.jpg
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I've reused rockers that look more like your second and third photo... I probably would had had the first one refinished or replaced. I will guess that someone on here will tell you to replace all of them, and they may not be wrong.

Makes sense that the rocker pitting is at the heel, because that is where the spring is most compressed so the forces are greatest. Me, I'd send them off to CGarr in Michigan, but that may not be such a good option for you. He has rejected a couple of mine as being too pitted for sensible regrinding and use. Buying a couple of new ones ought not to break the bank if all the rest are OK.

Isn't the cam thrust washer beveled on one side? I think I recall doping out why - what it bears upon is narrower than the shim side. I suspect you can just put them back in the correct order and orientation. The key on reassembly is confirming chain wheel parallelism, which is the function of the washers.

I've not seen mention of cylinders chipping out like that, but I've no experience with the 964. Maybe it is common? The seal is the inner surface of the cylinder pressing against the head. The seal ring is there as insurance, but useful insurance - Porsche's experiment with the 3.2s with the seal omitted and the top of the cylinder beveled for more compression of the mating surface seems not to have worked as well as hoped, so it was back to the CE ring.

If no on chimes in on this cylinder business, e-mail Henry Schmidt or Steve Weiner, both of whom graciously contribute to this forum from time to time..

I'll give them a bit longer to see this. In the meantime I'm tantalisingly close to splitting the case the hold ups are the piston wrist pins on pistons 4 through 6.

Pistons 1 through three were easy. I removed a circlips on each one and the wrist pins slid out with finger pressure.

Pistons 4 through 6 won't do the same. The wrist pins all look like they are hitting the piston. https://youtu.be/ytTTtgmMJJ8

Was I lucky with 1 through 3? Is some force required to extract these pins? I don't want to damage the pistons.

Hi John,
The chipping at the edge of the cylinder sealing surface is, I'm afraid, a result of the machining that was done to accept a sealing ring. This left a very thin surface at the edge. It could possibly be welded, bored and replated, but I would consider replacing the chipped cylinders myself. (I have an extra set of 964 cylinders and Pistons. PM me if you're interested.) As to the rockers, how do the cams look? Because the cams and rockers wear together, I have never been comfortable just replacing one or the other. My own 964 cams were started to show some spalling, so I had John Dougherty regrind them to. 993SS spec and also had all the rockers regrind.

Hi John,
I had Franklin cams in Auckland repair some cams for a 964, they refaced the rockers for me also. It was only a couple of weeks ago so they should remember. Give Brad a call and see if he can help you.

We may have some used cylinders here if you want me to have a look. Probably only the early type with no sealing groove.

Looks like your finding plenty of issues which is a shame.

Keep up the good work.

Cheers
Reuben

Thanks everyone for the above replies. It all helps as I clarify the way forward. The engine only leaked at one place, the nose bearing. It was leaking two litres of oil every 1,000 km so had to be sorted. I've split the case and am researching sealing options, of which there are manyhttp://forums.pelicanparts.com/uploa...1493233557.jpg

Btw the ugly item on the front of the bearing is a half removed Tom Amon collar. It is easier to remove when everything is disassembled.

Hi Reuben, thanks for that lead. As the cylinders don't appear to be leaking from the chips and everything else is good on them I'll likely refit them. If I get leaks I'll just pull it back down. It's only time.

Btw what is the oil passage machined into the block for? Mine was full of 574.

http://forums.pelicanparts.com/uploa...1493233834.jpg

It's an expensive motor to say the least; the items you have shown would be in my garbage bin, and I do this A LOT.

Henry at Supertec will get you awesome rebuilt rocker arms for $450 or something like that. Why take the chance.

I would never use those cracked cylinders, but that's just me.

A lot to mull over. Had the nose bearing not leaked so much I wouldn't have stripped the motor and found these issues. It's a car I intend to keep until I drop so it's worth doing right.

At a minimum I would need to source two good used cylinders and pistons with the right height group etc and may have to cut sealing grooves in them if my heads have been altered (I'm not sure if they have).

http://forums.pelicanparts.com/uploa...1493636644.jpg
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Those cylinders are easily found. Try autobahn dismantlers in San Diego, they get all of Singer's stuff that isn't used on the cars.

They were great when I needed a single cylinder head replacement. Great service, very nice packing, even compared to new.

Mike

I have been out on the hunt for used cylinders. As per the manual the cylinders must match the height group I.e. 6.

The question left unanswered is whether the piston weight group is critical as well? I would have one new cylinder and piston on each bank.

Well, you do want to match the piston weight group as well. However, if you can get a piston in a heavier weight group, it isn't all that hard to shave off some weight to get within the weight group range.

I see no one has opined on that grooved passage in the case for which you posted a picture. My belief is that it is there to allow oil which might otherwise try to escape out of the case at the parting line to have an easier path to drain back into the case, where it won't cause trouble.

Were I more knowledgeable or diligent I could find a diagram which shows which of the case through bolt passages are also passages for oil under pressure. And it may be the only such passage which has the outer side of the case as the next place for oil to go if it leaks - most of the bearing saddles, should they leak (Porsche doesn't seal the bearing saddles other than at the ends of the case, but some engine builders do) they will do so into the engine. Leaks like that are so small they won't affect oil pressure.

My engine reassembly mentor cautioned me to be careful with the sealant (he, and thus I, use the orange 574, which you can put on very thin if you take the trouble to do so)around this area so as not to fill it with sealant.

But it may be this was Porsche anticipating a problem which never really is a problem?

Thanks. The existing ones are the lower weight range so heavier ones could be trimmed. I'm thinking about balancing the lot.

You are 100% correct. The other joints can leak into the case. This joint could leak outside the case so the channel provides a path to leak back into the case. It should be left clear of sealant.